236 BRITISH SEA GBIRDs. 
does not obtain much food upon them. _ Its food is 
principally composed of marsh grass, and to obtain 
this it comes up from the sea to the saltings, and the 
banks of lakes and tidal rivers. Its flight and 
actions generally very closely resemble those of the 
Brent Goose. The note is similar. Nothing is 
known of the breeding grounds or the nesting 
habits of the Bernacle Goose. It has, however, 
been known to breed in confinement. The eggs 
are creamy white. 
SWANS. 
These large and handsome birds form the small 
but well-defined sub-family Cygnine. They may 
be distinguished from all other species in the 
ANATID&, by having the lores, or space between the 
eye and the base of the bill, bare of feathers, and 
by their reticulated tarsus. In this sub-family, as in 
the Anserinz, the sexes are nearly alike in colour. 
Swans moult only once in the year, in autumn. 
The young birds—known as Cygnets—are hatched 
covered with down, and able to swim. In first 
plumage they are uniform grayish- brown; and, 
unlike the Geese, they appear not to undergo any 
moult during their first autumn, but after the moult, 
which takes place in their second autumn, they 
acquire the pure white plumage of the adult. 
Although this sub-family contains but seven species, 
probably all referable to one genus, its distribution 
is wide, embracing the Palzearctic, Nearctic, Neo- 
tropical, and Australian regions. Besides the Mute 
